Molding a guiding tube for medical instruments

ABSTRACT

A method for molding a tube for guiding a rod-like medical instrument into a living body, which includes a tubular body made of a synthetic resin and having a longitudinal hollow portion to permit the passage of the rod-like medical instrument. The whole of the tubular body is formed to have a chemical uniformity, but at least one brittle portion such as a weld line is longitudinally formed over the entire length (or almost the entire length except tip portion) of the tubular body.

BACKGROUND OF THE INVENTION

The present invention relates to a synthetic resin tube for guiding arod-like medical instrument such as a catheter and a guide wire into,for example, a blood vessel and for keeping the medical instrumentattached to the blood vessel.

A flexible tube of synthetic resin is generally used for guiding, forexample, a catheter into a blood vessel and for keeping the catheterattached to the blood vessel. As shown in FIG. 8, a guiding tube 1 ismounted to a syringe 2 such that the tip of an inner needle 3 of thesyringe 2 projects outward through the tip of the guiding tube 1. Then,the inner needle 3 is inserted into a blood vessel 4 until the tip ofthe guiding tube 1 is positioned within the blood vessel 4, as shown inFIG. 9. Under this condition, the inner needle 3 is withdrawn from theblood vessel 4, with the guiding tube 1 kept attached to the bloodvessel 4. Further, a desired catheter 5 is inserted into the guidingtube 1 until the tip of the catheter 5 is positioned within the bloodvessel 4, as shown in FIG. 10. After the catheter 5 has been attached tothe blood vessel 4 as desired, it is desirable to withdraw the guidingtube 1 from the blood vessel 4 and from the catheter 5. It is sanitarilyundesirable to leave the guiding tube 1 unremoved after use. Also, theguiding tube left unremoved after use hinders the operation of thecatheter 5. However, the presence of an enlarged portion, such as aconnector 6 of the catheter, makes it quite difficult to withdraw theguiding tube 1 from the catheter 5.

Several measures have been proposed to date for withdrawing the guidingtube 1 after use from the catheter 5. For example, it has been proposedto provide the guiding tube with a longitudinal slit to enable theguiding tube after use to be readily removed from the catheter. However,serious problems are brought about in this case. For example, thestrength of the guiding tube is lowered, making it troublesome tooperate the guiding tube. Also, the slit of the guiding tube is likelyto expand when the catheter is inserted through the guiding tube into ablood vessel, leading to a leakage of blood. To overcome the problem, itis unavoidable to make the slit narrow with the result that removal ofthe guiding tube from the catheter remains difficult.

Japanese Patent Disclosure (Kokai) No. 56-11069 proposes anothermeasure. Specifically, it is proposed that a guiding tube is providedwith a pair of linear bodies extending along the length of the guidingtube and positioned opposite to each other in the radial direction ofthe guiding tube. The linear body is formed of a plastic materialforeign to the material forming the main body of the guiding tube. Also,the proximal end portion of the guiding tube, which is joined to theinner needle hub, of the guiding tube is provided with a pair of slitsaligned with the linear bodies. After a catheter or the like insertedthrough the guiding tube has been attached to a blood vessel, theproximal end portion of the guiding tube is pulled outward in oppositedirections. As a result, the guiding tube after use is split into twoparts along the linear bodies. Of course, the slits formed in theproximal end portion of the guiding tube facilitate the splitting. Inthis proposal, however, the linear body tends to be cracked during theafter-treatment, such as cutting or edge-processing of the guiding tube,or during transport or the like of the product guiding tube, with theresult that leakage of blood is likely to take place so as to make theguiding tube unsuitable for use.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a guiding tube forrod-like medical instruments such as a catheter, which is free fromaccidental splitting or cracking during the after-treatment in themanufacture of the guiding tube or during a handling of the guidingtube. Another object of this invention is to provide a guiding tubewhich can be easily removed from, for example, a catheter after thecatheter inserted through the guiding tube has been attached to a bloodvessel.

According to an aspect of the present invention, there is provided atube for guiding rod-like medical instruments into a living body,comprising a tubular body formed of synthetic resin in a hollow shapecapable of positioning the rod-like medical instruments, and at leastone brittle portion formed so that the splitting strength thereof issmaller than the other portion over the entire length of longitudinaldirection of the tubular body or the entire length of the longitudinaldirection of the tubular body except the end thereof and formed of thesame material as the other portion.

According to another aspect of the present invention, there is provideda method of producing a tube for guiding rod-like medical instrumentsinto a living body having a tubular body formed of synthetic resin in ahollow shape capable of positioning the rod-like medical instruments,and at least one brittle portion formed so that the splitting strengththereof is smaller than the other portion over the entire length oflongitudinal direction of the tubular body or the entire length of thelongitudinal direction of the tubular body except the end thereof andformed of the same material as the other portion, comprising the stepsof substantially temporarily splitting the synthetic resin flow at leastby one or more baffles arranged near a nozzle of a die of an extruder ofa molding resin passageway in the vicinity of the nozzle of the die ofthe extruder, then recombining the split resin flows, and extruding themolding resin flow from the nozzle of the die while molding as thebrittle portion.

According to still another aspect of the present invention, there isprovided an apparatus for producing a tube for guiding rod-like medicalinstruments into a living body, comprising a tubular body formed ofsynthetic resin in a hollow shape capable of positioning the rod-likemedical instruments, and at least one brittle portion formed so that thesplitting strength thereof is smaller than the other portion over theentire length of longitudinal direction of the tubular body or theentire length of the longitudinal direction of the tubular body exceptthe end thereof and formed of the same material as the other portion,comprising at least one or more baffles provided in the vicinity of thenozzle of the die having an annular sectional molding resin passagewayfor temporarily substantially splitting the synthetic resin flow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a guiding tube for medicalinstruments according to one embodiment of the present invention;

FIG. 2 is a sectional view along line II-II of FIG. 1;

FIG. 3 is a perspective view showing the guiding tube of FIG. 1longitudinally split into two parts along linear body from one endthereof;

FIG. 4 is a view showing a front face of an extrusion molding machinefor the tube of FIG. 1;

FIG. 5 is a sectional view showing the extrusion molding machine of FIG.4;

FIG. 6 is a view showing the front face of another embodiment of theextrusion molding machine of FIG. 4;

FIG. 7 is a sectional view of the extrusion molding machine of FIG. 6;and

FIGS. 8 to 10 are schematic views describing prior art guiding tube formedical instruments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As seen from FIGS. 1 to 3, guiding tube 11 for medical instrumentsaccording to one embodiment of the present invention comprises a tubularbody opened at opposite ends in the shape of a hollow tube for guiding arod-like medical instrument such as a catheter and converged at one endin contact with an inner needle, not shown, and enlarged at the othercylindrical base.

The tubular body is formed, as shown in FIG. 2, with brittle portions12a and 12b so made at two parts of the circle of the body, i.e., at twopositions opposite to each other in the radial direction along thelength of the tubular body or along the entire length of the body exceptthe opposite end that the splitting strengths are smaller than those ofthe other circular portion.

Brittle portions 12a and 12b of the tubular body are formed withextrusion molding machine or extruder 13 as shown, for example, in FIGS.4 and 5. Molding machine 13 comprises a pair of baffles 15a and 15b sopositioned oppositely to each other on the inner peripheral surface ofinner die 16 and projected oppositely from the inner peripheral surfaceof die 16 in the radial direction in annular passageway 18 in thevicinity of a nozzle of annular die 14 that the molded parts of thetubular body passing baffles 15a and 15b naturally become brittleportions 12a and 12b.

Baffles 15a and 15b may be determined at the positions and in theheights properly in relation to the type and the mixture of syntheticresin to be used. When distance L between the end positions of baffles15a and 15b and the end of die 14 is 0 to 5 mm and distance h betweenthe upper ends of baffles 15a, 15b and the inner wall of die 17 is setto h: H=0 to 1/2: 1, preferably 0 to 1/5: 1 to the interval H of resinpassageway 18, brittle portions 12a, 12b having desired splittingstrength are provided.

When the tubular body of the guiding tube for the medical instrument ismolded by the extruder provided with baffles 15a and 15b near the nozzleof die 14 under the above-mentioned conditions, softened resin guidedinto die 14 by a screw, not shown, is fed in die 14 temporarilysubstantially split state by baffles 15a, 15b, is again bonded to eachother in the nozzle or in the vicinity of the nozzle of die 14 to bemolded in a tubular shape.

The tubular body thus molded is formed substantially smoothly at aglance in a continuous circular shape, but is formed with welding lines,i.e., brittle portions 12a, 12b in the portions passing baffles 15a,15b. Since brittle portions 12a, 12b remarkably decrease in bondingstrength between synthetic resins of other circular portion, portions12a, 12b are readily broken by applying an external stress thereto, andare, for example, readily split as shown in FIG. 3.

The splitting strength of brittle portions 12a, 12b may be regulated byadjusting the positions, the heights and the widths (lengths orthicknesses) of baffles 15a, 15b or arbitrarily adjusting the mixture oftwo or more resins.

Thermoplastic resins such as polypropylene, fluorinated plastics,chlorinated polyethylene, blend polymer of polyolefin resin andethylene/vinyl acetate copolymer are used properly selectively as thematerial of the tubular body of the guiding tube for the medicalinstruments.

The case that the extruder in which baffles 15a, 15b are projected onthe inner die has been used has been described as shown in FIGS. 5 and6. However, the present invention is not limited to the particularembodiment. Various other changes and modifications may be made withinthe spirit and scope of the present invention. In the embodimentdescribed above, other arbitrary molding means may be employed. Forexample, as shown in FIGS. 6 and 7, the same baffles 15a, 15b as thosewhich have been described with reference to FIGS. 4 and 5 may bepositioned oppositely to the annular die 14 (in which symbols designateall the same as those in FIGS. 4 and 5). Further, though not shown,similar baffles may be projected oppositely to annular and inner dies.In any case, the positions (L), the heights (h) and the sizes of thebaffles may be regulated and selected similarly to the case of FIGS. 4and 5.

A method of using the guiding tube for the medical instrument of thepresent invention will be described.

Guiding tube 11 of the present invention is, for example, mounted tosyringe 2 as shown in FIG. 8 with respect to guiding tube 1, and is thenpositioned together with the inner needle of syringe within a bloodvessel, as shown in FIG. 9. Under this condition, inner needle 3 iswithdrawn from the blood vessel, with guiding tube 11 kept attached toblood vessel 4. Then, a catheter is inserted into guiding tube 11 sothat catheter is positioned within the blood vessel.

Then, in withdrawing guiding tube 11 after use from the catheter, anexternal stress is applied to guiding tube 11 as shown in FIG. 3 to cutthe base ends of brittle portions 12a, 12b, and tube 11 is split throughthe base ends of brittle portions 12a, 12b. Then, guiding tube 11 can bereadily withdrawn from catheter 5.

In the embodiments described above, the catheter has been guided as theguiding tube for the medical instruments. However, the present inventionis not limited to the catheter, but may be applied to the case that alltypes of rod-shaped medical instruments are positioned within a livingbody.

The above-mentioned brittle portions to be split are not limited to thetwo linear bodies as in the embodiments described above, but may beprovided with one or three or more linear bodies of the brittleportions.

The guiding tube for the medical instrument according to the presentinvention as described above is not necessarily provided with the linearbodies formed of a synthetic resin foreign to the material forming thetubular body of the guiding tube as the conventional art but is moldedof a sole plastic composition. Thus, the linear body can avoid to beunintentionally cracked during the after-treatment, such as cutting oredge-processing of the guiding tube, the guiding tube can bemanufactured readily, leading to a low manufacturing cost of the guidingtube.

EXAMPLE 1

A pair of baffles having 22 mm long and 0.5 wide were provided, as shownin FIG. 7, in contact with the inner wall of the inner die at theannular die of an extruder so that the tip thereof was disposed at theposition of 0.5 mm before the nozzle of the die (i.e., "L"=0.5 mm inFIG. 7). Then, a guiding tube fitting a 16G inner needle was prepared bypolypropylene. Even when the tip of the guiding tube was processed incontact with the 16G inner needle, the guiding tube was found to be freeof problems such as cracking of the tip portion. Also, the pin portionof the guiding tube was free from roughening, cracking, etc. when theguiding tube was stuck in a blood vessel of a dog together with theinner needle. Further, the linear body was readily peeled from thetubular body in removing the guiding tube.

COMPARISON EXAMPLE 1

A catheter guiding tube was prepared by extrusion molding similarly tothe Example 1 except that the similar baffles to those in the Example 1were disposed at a position of 6 mm before the nozzle of the die.However, in this case, the guiding tube was not substantially moldedwith brittle portions and could not be split.

COMPARISON EXAMPLE 2

Similar baffles to those of the Example 1 were projected on the innerwall of the annular die having 5 mm of inner diameter. However, in thiscase, the heights of the baffles were separated 0.6 mm from theperipheral surface of the inner die having 4 mm of outer diameter, andthe ends of the baffles were positioned 0.5 mm before the nozzle of thedie. When a catheter guiding tube was molded similarly to the Example bythis extruder, a brittle portion was not substantially molded and theguiding tube could not be split.

What is claimed is:
 1. A method of producing a synthetic resin tube for guiding rod-like medical instruments into a living body, having a tubular body with a circular hollow transverse cross section of a uniform thickness and being capable of positioning the rod-like medical instruments, and having at least one brittle portion and another portion, said at least one brittle portion being formed so that the splitting strength thereof is smaller than the splitting strength of said other portion over at least the entire length of the tubular body except the end thereof, said at least one brittle portion being formed of the same material as the other portion, comprising the steps of:forming a split portion of resin flow by substantially temporarily splitting flow of a synthetic resin flowing in a resin flow passageway inside a nozzle of a die of an extruder with at least one baffle; arranging said at least one baffle to extend radially inside said nozzle and recessed 0 to 5 mm axially from an end of said nozzle, the height of the at least one baffle being at least 1/2 of a height of said resin flow passageway of the die; and extruding the resin flow from a nozzle of the die, while recombining the split portion of the resin flow to forming the brittle portion of the resin tube at the split portion of the resin flow.
 2. A method according to claim 1, wherein the height of the at least one baffle is at a ratio of 0 to 1/5 to a height of 1 of said flow passageway. 